1. Field of the Invention
The present invention relates in general to the deposition of carbon coatings on substrates by carbon sputtering through ion bombardment and to a new and useful device and method for producing carbon coatings by sputtering.
2. Description of the Prior Art
Because of their resistance to most of the chemical agents and to high temperatures, carbon coatings are applicable to many purposes, for example, they are largely used as protective layers, for electrical layer resistors, as well as in the technique of making preparations for electron microscopes.
The sputtering of substances through ion bombardment in an electrical gas discharge or by ions from a so-called ion gun, and depositing of the sputtered particles on a substrate to form a coating, has been well known for a long time. This method has proved satisfactory particularly in the form of a so-called cathode sputtering. Most of the solid substances can be sputtered, among them also the metals difficult to fuse because of the required high temperatures, such a molybdenum or tungsten. With carbon, however, the experience has been, up to the present time, that in the usual manner, this substance is very difficult to sputter, irrespective of the discharge conditions, i.e. the voltage and amperage of the discharge current, pressure in the sputtering space, or gas in which the sputtering takes place. Therefore, the sputtering rate obtainable with carbon has not been interesting for most of the technical applications. On the other hand, for many purposes, carbon layers deposited in this way would be more satisfactory than layers deposited by vacuum evaporation, since in a sputtering process, they can be made denser and more uniform. In spite of that, carbon layers have hitherto been produced frequently by evaporation of carbon between carbon electrodes or by means of an electron gun.